Kinetic effects and nonlinear heating in intense x-ray-laser-produced carbon plasmas

Area of Science:

• Plasma Physics
• Laser-Matter Interaction
• Computational Physics

Background:

• Understanding x-ray laser-matter interactions is crucial for high energy density physics.
• Low-Z materials like carbon are fundamental in many physical processes.
• Previous studies often simplified the complex interplay of photoionization and transport.

Purpose of the Study:

• To investigate the self-consistent interaction of x-ray lasers with carbon.
• To characterize the resulting plasma state, including temperature, energy density, and coupling parameters.
• To explore the influence of laser parameters on plasma properties.

Main Methods:

• Utilized a particle-in-cell code for self-consistent simulation.
• Modeled photoionization as the primary absorption mechanism.
• Analyzed x-ray transport and subsequent plasma evolution.

Main Results:

• Photoionization dominates absorption, generating nonthermal photoelectrons.
• Photoelectrons drive rapid ionization, forming a hot plasma column.
• Heated region expands radially beyond the laser spot size.
• Achieved strongly coupled warm dense matter (T>10,000 K, Γ≥1, Θ≥1).
• Plasma temperature scales nonlinearly with laser intensity, reaching the high energy density regime.
• Heating depth and temperature are tunable via laser photon energy.

Conclusions:

• X-ray laser interactions with carbon can create strongly coupled warm dense matter.
• Laser intensity and photon energy offer control over plasma parameters.
• The kinetic nature of photoelectrons significantly influences the heated region's size.